Silicone antifoaming agent

ABSTRACT

Silicone antifoaming agent of the present invention demonstrates excellent antifoaming effect with regard to aqueous foaming systems, and is especially suitable for use in conjunction with inks where it significantly suppresses development of cissing during use of ink. The silicone antifoaming agent is characterized by comprising a polyoxyalkylene-modified silicone that has polyoxyalkylene groups expressed by general formula (1) and (2) given below and contains 10 to 200 diorganosiloxane units in one molecule, said polyoxyalkylene-modified silicone satisfying the following conditions: 3≦E≦90 and 0.01≦E/(E+P)≦0.45, wherein P is the total number of oxypropylene units (—C 3 H 6 O—) and E is the total number of oxyethylene units (—C 2 H 4 O—) contained in one molecule.

TECHNICAL FIELD

[0001] The present invention relates to a silicone antifoaming agentthat can demonstrate an excellent antifoaming effect, e.g., with respectto aqueous ink or a similar water-based system.

BACKGROUND ART

[0002] Polyoxyalkylene-modified silicone is characterized by manypositive properties, such as low surface tension, high thermal andchemical stability, etc., and therefore this compound finds wideapplication in various fields in the form of foaming stabilizers,cosmetic additives, coating leveling agents, antifoaming agents, etc.Polyoxyalkylene groups suitable for modification consist of hydrophilicpolyoxyelthylene groups (EO) and hydrophobic polyoxypropylene groups(PO). By varying an EO to PO ratio, it is possible to vary eitherpolyoxyalkylene groups or a balance between hydrophilic and hydrophobicproperties of the modified silicone oil. An antifoaming agent thatcontains a polyoxyalkylene-modified silicone is described, e.g., inJapanese Laid-Open Patent Application [Kokai] H5-57109, U.S. Pat. No.5,271,868 and U.S. Pat. No. 5,804,099.

[0003] However, known antifoaming agents used for aqueous foamingsystems need further improvement to enhance antifoaming performances. Itis especially important and strongly desirable in ink application toprovide highly performing antifoaming agent which does not causecratering & cissing (so-called fish eye) when the ink compositioncontaining an antifoaming agent is applied onto a substrate such anpaper.

DISCLOSURE OF INVENTION

[0004] The above problems are solved by means of the siliconeantifoaming agent of the invention. More specifically, thesilicone-antifoaming agent of the invention comprises apolyoxyalkylene-modified silicone that contains 10 to 200diorganosiloxane units per molecule and has polyoxyalkylene-modifyinggroup expressed by general formula

—(CH₂)_(r)-O—(C₃H₆O)s-Q  (1),

[0005] where Q is a hydrogen atom, or a monovalent organic groupselected from an alkyl group having 1 to 18 carbon atoms, an acyl group,an amino group that can be substituted, or an —N═C═O group, r is anumber from 2 to 6, and s is a number from 5 to 50,

[0006] and polyoxyalkylene) group expressed by general formula

—(CH_(2 r′)-O—(C₂H₄O)_(s′)-Q′  (2),

[0007] where Q′ is a hydrogen atom, or a monovalent organic groupselected from an alkyl group having 1 to 18 carbon atoms, an acyl group,an amino group that can be substituted, or an —N═C═O group, r′ is anumber from 2 to 6, and s′ is a number from 1 to 30,

[0008] said polyoxyalkylene-modified silicone satisfying the followingconditions:

[0009] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0010] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene units (—C₂H₄O—) per molecule.

[0011] A polyoxyalkylene-modified silicone is a known compound, which isnormally synthesized by the methods described below. It can be obtainedby binding structures formed by interconnecting 1 to 10, or more,repeating units made up of oxyalkylene groups to some silicon atoms onthe main chain or to terminal silicon atoms of the diorganopolysiloxanevia alkylene groups.

[0012] A preferable antifoaming agent composed of apolyoxyalkylene-modified silicone of the invention can be expressed bythe following general formula (3):

R¹ _(3-a)G¹ _(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹_(a)R¹ _(3-a)  (3)

[0013] where G¹ is a group selected from R¹, G² or G³, which can bedifferent, and R¹ is independently an alkyl group with 1 to 18 carbonatoms or an aromatic group with 6 to 9 carbon atoms,

[0014] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0015] (where Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 11 to 18 carbon atoms, an acylgroup, an amino group, that can also be substituted, or a —N═C═O group,r is a number from 2 to 6, and s is a number from 5 to 50), and

[0016] G³ is a group represented by the following formula:

—(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′

[0017] (where Q′ is the same as Q, r′ is a number from 2 to 6, and s′ isa number from 1 to 30);

[0018] x is a number from 10 to 200, y is a number from 0 to 60, z is anumber from 0 to 30; and a is 0 or 1,

[0019] said polyoxyalkylene-modified silicone satisfying the followingconditions:

[0020] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0021] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene units (—C₂H₄O—) per molecule.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] A polyoxyalkylene-modified silicone that constitutes a siliconeantifoaming agent of the present invention may be modified withpolyoxyalkylene groups of two different types. The first type relates topolyoxypropylene groups expressed by aforementioned general formula (1),and the second the second type relates to polyoxyethylene groupsexpressed by aforementioned general formula (2).

[0023] A polyoxyalkylene-modified silicone normally consists ofdiorganopolysiloxane units without polyoxyalkylene-modifying groups,organopolysiloxane units with polyoxyalkylene-modifying groups, andterminal groups (normally, triorganosiloxy groups or siloxy groups withpolyoxyalkylene-modifying groups).

[0024] The polyoxyalkylene-modified silicone of the present inventionmay have polyoxyalkylene-modifying groups only on siloxane units of themain chain, or instead of polyoxyalkylene-modifying groups on siloxaneunits of the main chain, respective polyoxyalkylene-modifying groups canbe bonded to both siloxy groups on both terminals of the aforementionedpolyoxyalkylene-modified silicone, or the polyoxyalkylene-modifyinggroups can be bonded to both the main chain and the terminals.

[0025] Group Q, which is a terminal group of thepolyoxypropylene-modifying group of formula (1), may comprise amonovalent organic group and may be selected from an alkyl group having1 to 18 carbon atoms, an acyl group, an amino group that can also besubstituted, and an —N═C═O group (isocyanato group). Here, the alkylgroups can be exemplified by methyl, ethyl, propyl, butyl, hexyl,heptyl, and octyl groups. The alkyl groups may have a linear or abranched structure, but if the number of carbon atoms exceeds 18, theantifoaming polyoxyalkylene-modified silicone oil that contains suchalkyl groups will have a viscosity increased to a level at which theantifoaming agent becomes unsuitable for use with aqueous foamingsystems.

[0026] Acyl groups can be exemplified by acetyl, acryloyl, methacryloyl,or similar groups. In addition to —NH₂, other amino groups, that canalso be substituted, are alkylamino, dialkylamino or similar groups. Asuitable example of Q is an alkyl group having 1 to 6 carbon atoms. Inthis case, in formula (1), r should be between 2 and 6, and s should bebetween 5 and 50, and preferably, between 10 and 30.

[0027] On the other hand, Q′ that represents a terminal group of thepolyoxyethylene modifying group of general formula (2), may be the sameas Q defined above. Here, r′ should be between 2 and 6, and s′ should bebetween 1 and 30, and preferably, between 5 and 15.

[0028] If the number of diorganosiloxane units is less than the lowerlimit of the above-mentioned range (10 to 200 units), the antifoamingeffect of the antifoaming agent will be diminished because of anincrease in solubility of the agent in aqueous foaming systems. If, onthe other hand, the amount of the diorganosiloxane units exceeds theupper limit of the above-mentioned range, this will impair compatibilityof the silicone antifoaming agent with aqueous foaming systems, and whensuch an agent is used in conjunction with ink, the ink applied onto asubstrate will demonstrate cissing. Therefore, the preferable number ofdiorganosiloxane units is within the range from 50 to 150.

[0029] If the total number E of oxyethylene units in one molecule isbelow the lower limit of the above-mentioned range (which is 3 to 90),this will impair compatibility of the silicone antifoaming agent withaqueous foaming systems. For example, if in this case the siliconeantifoaming agent is used with ink, the ink applied onto a substratewill demonstrate cissing. If, on the other hand, the amount of thediorganosiloxane units exceeds the upper limit of above-mentioned range,the antifoaming effect will be reduced because of an increasedsolubility of the antifoaming agent in aqueous systems.

[0030] In view of the above, it is preferable that total number ofoxyethylene units in one molecule be within the range of 10 to 70.

[0031] If E/(E+P), the ratio of oxyethylene units to a total number ofboth oxyethylene and oxypropylene units contained in one molecule, isbelow the lower limit of the above-mentioned range (which is from 0.01to 0.45), this will impair affinity between the silicone antifoamingagent and the aqueous foaming system. As a result, when this agent isused in conjunction with ink, the ink applied onto a substrate willdemonstrate cissing. If, on the other hand, the E/(E+P) ratio exceedsthe upper limit of the above-mentioned range, the silicone, antifoamingagent will become easily soluble in an aqueous foaming system, wherebythe antifoaming effect of the agent will decrease. It is preferable thatthe E/(E+P) ratio be within the range of 0.1 to 0.35.

[0032] A silicone antifoaming agent comprising apolyoxyalkylene-modified silicone of the present invention satisfieswith the conditions described above, and the preferable one may beexpressed by aforementioned general formula (3). The G¹ in formula (3)is a group selected from R¹, G², or G³. R¹ can be independently an alkylgroup with 1 to 18 carbon atoms or an aromatic hydrocarbon group with 6to 9 carbon atoms. The aforementioned alkyl group may have a linear or abranched structure. It can be represented, e.g., by a methyl, ethyl,propyl, butyl, hexyl, heptyl, octyl, or a similar group, preferably with1 to 6 carbon atoms. An example of the aforementioned aromatichydrocarbon group includes a phenyl group and the like.

[0033] G² is expressed by the following formula: —(CH₂)_(r-O—(C)₃H₆O)_(s)-Q, where Q, r, and s are the same as defined above.

[0034] In general formula (3), x is between 10 and 200, preferablybetween 50 and 150, y is between 0 and 60, preferably between 1 and 20,s is between 0 and 30, preferably between 1 and 10, and a is 0 or 1.

[0035] It is required, as has been mentioned earlier, that inaforementioned formula (3) the following conditions are satisfied:3≦E≦90 and 0.01≦E/(E+P)≦0.45, where P is the total number ofoxypropylene units (—C₃H₆O—) and E is the total number of oxyethyleneunits (—C₂H₄O—) contained in one molecule.

[0036] As has been mentioned above, the polyoxypropylene-modifyinggroups and polyoxyethylene-modifying groups can be bonded either to themain chain or to the terminals of the polyoxyalkylene-modified silicone.For example, a structure within the scope of the present invention mayhave a polyoxypropylene-modifying group bonded to silicon atom of asiloxy group on one terminal, and a polyoxyethylene-modifying groupbonded to silicon atom of a siloxy group on another terminal, while asiloxane unit of the main chain may be without any polyoxyalkylenemodifying group at all. This case has the formula (3), where y=0 andz=0.

[0037] In other words, when y=0 or z=0, at least one terminal siloxygroup has a=1, and when y=z=0, both terminal siloxy groups have a=1.

[0038] It is recommended that the number of oxypropylene units (—C₃H₆O—)of polyoxypropylene groups bonded to silicon atom of siloxane units viaan alkylene group is within the range of 5 to 50. If this number is lessthan the lower limit of the recommended range, the effect of theantifoaming agent will be diminished, and if this number exceeds theupper limit, the polyoxyalkylene-modified silicone will have anincreased viscosity that will impair dispersibility of the agent in thefoaming system. It is more preferable that the number of saidoxypropylene units be within the range of 10 to 30.

[0039] It is recommended that the number of oxyethylene units (—C₂H₄O—)of oxyethylene groups bonded to silicon atom of siloxane units viaalkylene groups is within the range of 1 to 30. If this number exceedsthe upper recommended limit, it would be impractical since thepolyoxyalkylene-modified silicone will exhibit a strong tendency tosolidification. Most preferable number of aforementioned oxyethyleneunits is within the range of 5 to 15.

[0040] Furthermore, from the point of view of synthesis, it is necessaryto select the number of siloxane units with polyoxypropylene groupsbonded via alkylene groups within the range of 0 to 60, preferably of 1to 20. When the above number of siloxane units is 0, it is naturallyrequired that at least one siloxy group present at a main-chain terminalof the polyoxyalkylene-modified silicone containingpolyoxyethylene-modifying group has polyoxypropylene-modifying group.

[0041] It is recommended that the number of siloxane units, havingoxyethylene groups bonded via alkylene groups, be within the range of 0to 30. If this number exceeds the upper limit of the recommended range,antifoaming capacity will be impaired due to an increase in solubilityof the agent in an aqueous foaming system. It is preferable that theaforementioned number be within the range of 1 to 10. When the number ofthe aforementioned siloxane units is 0, it is naturally required that atleast one siloxy group present at a main-chain terminal of thepolyoxyalkylene-modified silicone containing polyoxypropylene-modifyinggroup has polyoxyethylene-modifying group.

[0042] For use in aqueous foaming systems, it is preferable that thepolyoxyalkylene-modified silicone contained in the antifoaming siliconeagent of the invention has viscosity from 10 to 100,000 cSt.

[0043] The invention will be further described with reference topreferably practical embodiments.

Practical Embodiment 1

[0044] Silicone antifoaming agent composed of polyoxyalkylene-modifiedsilicone of general formula (4)

R¹ _(3-a)G¹ _(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹_(a)R¹ _(3-a)  (4)

[0045] [where G¹ is a group selected from R¹, G², or G³, where R¹ isindependently an alkyl group with 1 to 6 carbon atoms or an aromaticgroup with 6 to 9 carbon atoms;

[0046] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0047] (where Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 1 to 6 carbon atoms, an acyl group,an amino group that can also be substituted, or isocyanato; r is anumber from number from 2 to 6, and s is a number from 5 to 50); and

[0048] G² is a group represented by the following formula:

—(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′

[0049] (where Q′ is the same as Q, r′ is a number 2 to 6, and s′ is anumber from 1 to 30); x is a number from 10 to 200, y is a number from 1to 60, z is a number from 1 to 30, and a is 0.

[0050] however, there is a limitation consisting in that the followingconditions should be observed:

[0051] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0052] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene unite (—C₂H₄O—) contained in onemolecule.]

Practical Embodiment 2

[0053] Silicone antifoaming agent composed of polyoxyalkylene-modifiedsilicone of general formula (5)

R¹ _(3-a)G¹ _(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹_(a)R¹ _(3-a)  (5)

[0054] [where G¹ is a group selected from R¹, G², or G³, where R¹ isindependently an alkyl group with 1 to 6 carbon atoms or an aromaticgroup with 6 to 9 carbon atoms;

[0055] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0056] (where Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 1 to 6 carbon atoms, an acyl group,an amino group that can also be substituted, or isocyanato r is a numberfrom 2 to 6, and s is a number from 5 to 50); and

[0057] G² in a group represented by the following formula:

—(CH₂)_(r′)-O—(C₃H₆O)_(s′)-Q′

[0058] (where Q′ is the same as Q, r′ is a number from 2 to 6, and s′ isa number from 1 to 30); x is a number from 10 to 200, y is a number from0 to 60, z is a number from 0 to 30, and a is 1.

[0059] however, there is a limitation consisting in that the followingconditions should be observed:

[0060] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0061] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene units (—C₂H₄O—) contained in onemolecule.]

Practical Embodiment 3

[0062] Silicone antifoaming agent composed of polyoxyalkylene-modifiedsilicone of general formula (6)

R¹ _(3-a)G¹ _(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹_(a)R¹ _(3-a)  (6)

[0063] [where one G¹ is G² and another G¹ is G³;

[0064] R¹ is independently an alkyl group with 1 to 6 carbon atoms or anaromatic group with 6 to 9 carbon atoms;

[0065] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0066] (where Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 1 to 6 carbon atoms, an acyl group,an amino group, that can also be substituted, or isocyanato; r is anumber from 2 to 6, and s is a number from 5 to 50); and

[0067] G³ is a group represented by the following formula:

—(CH₂)_(r′)-O—(C₃H₆O)_(s′)-Q′

[0068] (where Q′ is the same as Q, r′ a number from 2 to 6, and s′ is anumber from 1 to 30); x is a number from 10 to 200, y is 0, z is 0, anda is 1.

[0069] however, there is a limitation consisting in that the followingconditions should be observed;

[0070] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0071] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the number of oxyethylene units (—C₂H₄O—) contained in onemolecule.]

Practical Embodiment 4

[0072] Silicone antifoaming agent composed of polyoxyalkylene-modifiedsilicone of general formula (7)

R¹ _(3-a)G¹ _(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹_(a)R¹ _(3-a)  (7)

[0073] [where one G¹ is G² and another G¹ is G³;

[0074] R¹ independently an alkyl group with 1 to 6 carbon atoms or anaromatic group with 6 to 9 carbon atoms;

[0075] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0076] (where Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 1 to 6 carbon atoms, an acyl group,an amino group, that can also be substituted, or isocyanato; r is anumber from 2 to 6, and s is a number from 5 to 50);

[0077] G³ is a group represented by the following formula:

—(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′

[0078] (where Q′ is the same as Q, r′ is number from 2 to 6, and s′ is anumber from 1 to 30); x is a number from 10 to 200, y is a number from 1to 60, z is a number from 1 to 30, and a is 1.

[0079] however, there is a limitation consisting in that the followingconditions should be observed:

[0080] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0081] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene units (—C₂H₄O—) contained in onemolecule.]

Practical Embodiment 5

[0082] This is the same silicone antifoaming agent as in PracticalEmbodiment 1, except that in general formula (4) Q is an alkyl groupwith 1 to 6 carbon atoms, and Q′ is also an alkyl group with 1 to 6carbon atoms.

Practical Embodiment 6

[0083] This is the same silicone antifoaming agent as in PracticalEmbodiment 2, except that Q in general formula (5) is an alkyl groupwith 1 to 6 carbon atoms, and Q′ is also an alkyl group with 1 to 6carbon atoms.

Practical Embodiment 7

[0084] This is the same silicone antifoaming agent as in PracticalEmbodiment 3, except that Q in general formula (6) is an alkyl groupwith 1 to 6 carbon atoms, and Q′ is [also] an alkyl group with 1 to 6carbon atoms.

Practical Embodiment 8

[0085] This is the same silicone antifoaming agent as in PracticalEmbodiment 4, except that Q in general formula (7) is an alkyl groupwith 1 to 6 carbon atoms, and Q′ is [also] an alkyl group with 1 to 6carbon atoms.

Practical Embodiment 9

[0086] This is the same silicone antifoaming agent as in PracticalEmbodiment 2, except the Q in general formula (6) is an alkyl group with1 to 6 carbon atoms, Q′ is [also] an alkyl group with 1 to 6 carbonatoms, G¹ that substitutes a silicon atom of a siloxy group at oneterminal is G², and another G¹ that is bonded to silicon atoms ofterminal siloxy groups is also G², and z is a number from 1 to 30.

Practical Embodiment 10

[0087] This is the same silicone antifoaming agent as in PracticalEmbodiment 2, except that Q in general formula (6) is an alkyl groupwith 1 to 6 carbon atoms, Q′ is [also] an alkyl group with 1 to 6 carbonatoms, G¹ that substitutes a silicon atom of a siloxy group at oneterminal is G³, and another G¹ bonded to silicon atoms of terminalsiloxy groups is also G³, and y is a number from 1 to 60.

Practical Embodiment 11

[0088] A silicone antifoaming agent comprising apolyoxyalkylene-modified silicone characterized in that thepolyoxyalkylene-modified silicone consists of R¹SiO_(3/2) or SiO_(4/2)unit, and R¹ ₂SiO_(2/2), R¹ _(3-a)G¹ _(a)SiO_(1/2), R¹G²SiO_(2/2) andR¹G³SiO_(2/2) units, having totally 10 to 200 diorganosiloxane units permolecule,

[0089] where G¹ is a group selected from R¹, G², or G³, which can bedifferent, and R¹ is independently an alkyl group with 1 to 18 carbonatoms or an aromatic group with 6 to 9 carbon atoms;

[0090] G² is a group expressed by the following formula:

—(CH₂)_(r)-O—(C₃H₆O)_(s)-Q

[0091] in which Q is a hydrogen atom or a monovalent organic groupselected from an alkyl group having 1 to 18 carbon atoms, an acyl group,an amino group that can also be substituted, or an —N═C═O group, r is anumber from 2 to 6, and s is a number from 5 to 50;

[0092] G³ is a group represented by the following formula:

—(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′

[0093] in which Q′ is the same as Q, r′ is a number from 2 to 6, and s′is a number from 1 to 30); and a is 0 or 1,

[0094] said polyoxyalkylene-modified silicone satisfying the followingconditions:

[0095] 3≦E≦90 and 0.01≦E/(E+P)≦0.45,

[0096] wherein P is the total number of oxypropylene units (—C₃H₆O—) andE is the total number of oxyethylene units (—C₂H₄O—) per molecule.

[0097] The silicone antifoaming agent of the present invention can besynthesized by methods known as hydrosilylation reaction. For example,it can be obtained by causing an addition reaction between apolyoxyalkylene compound having a vinyl (or allyl) group on a terminalof the main molecular chain and an organohydrogenpolysiloxane (i.e.between unsaturated bond of the polyoxyalkylene compound and SiH bond ofthe organohydrogenpolysiloxane) in the presence of a platinum catalyst.

[0098] The polyoxyalkylene-modified silicone of the instant inventioncan be prepared by addition reacting the first polyoxyalkylene compoundhaving vinyl or allyl group, such as polyoxyethylene compound andpolyoxypropylene compound both having vinyl or allyl group, with theorganohydrogenpolysilxoane, followed by addition reaction of the secondpolyoxyalkylene compound having vinyl or allyl group, which is differentfrom the first polyoxyalkylene compound, with unreacted, remaining SiHbond of said organohydrogenpolysiloxane. When the first polyoxyalkylenecompound is polyoxyethylene compound, the second polyoxyalkylenecompound is selected from polyoxypropylene compound. Reverse is alsotrue. In those cases the first polyoxyalkylene compound should bereacted with the organohydrogenpolysiloxane, the mole ratio of thepolyoxyalkylene compound being less than mole of SiH bond in theorganohydrogenpolysiloxane to remain the unreacted SiH bond.

[0099] Alternatively the organohydrogenpolysiloxane can be reacted withsaid polyoxyethylene compound and said polyoxypropylene compoundsimultaneously.

[0100] The mole ratio of the polyoxyalkylene compound to theorganopolysiloxane may be determined, depending on what and how tostructure the polyoxylakylene-modified silicone to be desirable. Thereaction conditions will be also determined by simple pre-experiment.

[0101] The platinum catalyst for the hydrosilylation reaction is wellknown in this art. Japanese Patent Kokai No. 2001-114895 (equivalent toU.S. Pat. No. 6,211,323) is cited for this reference.

[0102] Regarding methods of application of the silicone antifoamingagent of the invention, its use is not limited only to aqueous foamingsystems and, if necessary, it can be used, e.g., in form of emulsion ofoil-in-water systems. In this case, it is recommended to use anemulsifying agent of a non-ionic type. The antifoaming agent of thepresent invention can be admixed with antifoaming agents of other types.Examples of such antifoaming agents are silicone compounds composed ofsilicone oil and silica. If necessary, the agent of the presentinvention can be used in combination with other silicone-type andorganic-type antifoaming agents.

[0103] There are no special limitations with regard to the amounts inwhich the antifoaming agents of the invention should be added to aqueousfoaming systems, and in each case the added amount is determined inaccordance with the required level of an antifoaming effect. In general,however, it should be added in an amount of 0.001 to 5% based on theweight of the aqueous foaming system.

PRACTICAL EXAMPLES

[0104] The invention will be further described in more detail withreference to practical examples, which, however, should not be construedas limiting the scope of the invention. In chemical formulae used in thepractical examples, Me stands for methyl groups.

Reference Example 1

[0105] (Synthesis of Polyoxyalkylene-Modified Silicone for Use inPractical Example 1)

[0106] A mixture was prepared from 29.57 g of organohydrogenpolysiloxanehaving SiH in a side molecular chain[Me₂SiO-(MeMeSiO)₅₅—(HMeSiO)₇—SiMe₃] and 3.49 g of a polyoxyethylenecompound [CH₂═CH—CH₂—(C₂H₄O)₁₁—CH₃]. The mixture was heated to 70° C.and combined with 0.06 g of a platinum catalyst (a 2 wt. % isopropylalcohol solution of chloroplatinic acid). The mixture was maintained at70° C., and 10 min. later a polyoxypropylene compound[CH₂═CH—CH₂—(C₃H₆O)₂₄—CH₃] was added in an amount of 66.94 g. Themixture was again combined with a 0.06 g of a platinum catalyst, heldfor 30 min. at 70° C. and filtered out, thus producing apolyoxyalkylene-modified silicone.

Reference Example 2

[0107] (Synthesis of Polyoxyalkylene-Modified Silicone for Use inPractical Example 8)

[0108] A mixture was prepared from 76.58 g of organohydrogenpolysiloxanehaving SiH only on both molecular chain terminals[HMe₂SiO-(MeMeSiO)₁₀₀—(SiMe₂H)] and 5.58 g of the polyoxyethylenecompound used in Reference Example 1. The mixture was heated to 70° C.and combined with 0.06 g platinum catalyst used in Reference Example 1.The mixture was maintained at 70° C., and 10 min. later 17.84 g of thepolyoxypropylene compound used in Reference Example 1 was added. Themixture was again combined with 0.06 g aforementioned platinum catalyst,held for 30 min. at 70° C. and filtered out, thus producing apolyoxyalkylene-modified silicone.

Practical Examples 1 to 10 and Comparative Examples 1 to 15

[0109] The tests described below were conducted with siliconeantifoaming agents and, for comparison, with other modified silicones,shown in Tables 1 and 2, respectively. The aforementioned siliconeantifoaming agents and modified silicones are expressed by the basicformulae shown below.

Practical Examples 1 to 7,9,10 and Comparative Examples 1 to 5,8,9,14

[0110] The polyoxyalkylene-modified silicone used therein has the basicstructural formula as follows:

[0111] G²: —(CH₂)₃—O—(C₃H₆O)s-CH₃

[0112] G³: —(CH₂)₃—O—(C₂H₄O)s′-CH₃

Practical Example 8

[0113] The polyoxyalkylene-modified silicone used therein has thestructural formula as follows:

Comparative Example 6

[0114] The polyoxyalkylene-modified silicone used therein has thestructural formula as follows:

Comparative Example 7

[0115] The polyoxyalkylene-modified silicone used therein has thestructural formula as follows:

Comparative Example 8

[0116] The polyoxyalkylene-modified silicone used therein has the basicstructural formula as follows:

Comparative Example 9

[0117] The polyoxyalkylene-modified silicone used therein has the basicstructural formula as follows:

[0118] Contents of the Test:

[0119] 1. Test of Antifoaming Capacity

[0120] Samples were prepared by loading 40 g of an aqueous ink having acomposition given below into a mayonnaise jar, and then 0.5% by weightof silicone antifoaming agent or an another silicone oil were added aseffective component. The components were mixed for 10 min. by means ofstirring blades rotating with the speed of 4000 rpm. Immediately afterstirring was stopped, density of the ink (g/cm³) was measured with theuse of a specific-gravity cup at 25° C. The same samples were retainedfor 2 days at 40° C. and then its density was measured in the samemanner. Those inks that had the density greater than 0.95 g/cm³ afterthe storage for 2 days at 40° C., can be called “passed the test”, butthose that had the density below 0.95 g/cm² can be called “failed”.

[0121] Aqueous ink composition: contained components (1) through (6)given below (all parts are by weight) (1) Pigment: Phthalo blue GNO-3*15 parts (2) Aqueous ink varnish: Joncryl 61J**  5 parts (3) Aqueous inkvarnish: Joncryl 7001** 40 parts (4) Polyethylene wax:  5 parts (5)Isopropyl alcohol:  5 parts (6) Water: 30 parts

[0122] 2. Compatibility Test (Draw Down Test)

[0123] The same samples as for antifoaming test were prepared, stirredin the same antifoaming tester, and then applied in the form of a 18.3μm-thick wet film onto a coat paper by means of a bar coater (No. 8)directly after stirring and after retaining at 40° C. for 2 days afterstirring. The coating was dried at room temperature for 10 min. and thenvisually observed to find if there is any cartering/cissing to determinethe compatibility of the antifoaming agent to the ink. Pass/non-passdecisions were also made with regard to the samples retained for 2 daysat 40° C.

[0124] O: Cratering/cissing absent (passed)

[0125] X: Cratering/cissing present (did not pass)

[0126] 3. Storage Test

[0127] The same samples as those prepared for the aforementionedantifoaming test and the aforementioned aqueous ink (without theantifoaming agent) were loaded into separate mayonnaise jars and held inan oven for 2 days at 40° C. The mayonnaise jars were placed onto atable and then inclined by 30° when the jar content was in a stablestate. The results of the tests were judged by visually observingwhether or not the sample in the jar has an extraordinary viscosityincrease.

[0128] O: Extraordinary viscosity increase not observed (no gelation)

[0129] X: Extraordinary viscosity increase observed due to gelation orthe like

[0130] Results of the aforementioned tests 1 to 3 are shown in Tables 3and 4. TABLE 1 Number of Total Total Number of —(MeG²SiO) Number ofnumber of number of —(Me₂SiO) units in 1 —(MeG³SiO) oxypropyleneoxyethylene units in 1 molecule units in 1 units in units in 1 molecule(y) molecule (z) 1 molecule molecule Molecular Pr. Ex. (x) s = 24 s′ =11 s′ = 6 z/(y + z) (P) (E) E/P + E) Weight 1 55.0 6.0 1.0 — 0.14 144 110.07 12,592 2 55.0 5.2 1.8 — 0.26 125 20 0.14 11,942 3 55.0 4.0 3.0 —0.43 96 33 0.26 10,968 4 55.0 3.5 3.5 — 0.50 84 39 0.32 10,562 5 33.02.0 1.0 — 0.33 48 11 0.19 5,736 6 14.4 2.0 1.0 — 0.33 48 11 0.19 4,322 770.0 2.0 1.0 — 0.33 48 11 0.19 8,548 8 100.0 0 0 — 0.50 24 11 0.31 9,5329 140.0 13.0 6.0 — 0.32 312 66 0.17 30,544 10 33.0 1.0 — 2.0 0.67 24 120.33 4,418

[0131] TABLE 2 Number of Total Total Number of —(MeG²SiO) Number ofnumber of number of —(Me₂SiO) units in 1 —(MeG³SiO) oxypropyleneoxyethylene units in 1 molecule units in 1 units in units in 1 molecule(y) molecule (z) 1 molecule molecule Molecular Comp. Ex. (x) s = 24 s′ =11 s′ = 6 z/(y + z) (P) (E) E/(P + E) Weight 1 6.0 1.0 — 1.0 0.50 24 60.20 2,135 2 247.0 18.0 9.0 — 0.33 432 99 0.19 46,608 3 110.0 20.0 10.0— 0.33 480 110 0.19 39,272 4 144.0 9.5 9.5 — 0.50 228 105 0.31 28,006 53.0 3.3 1.7 — 0.34 79 19 0.19 5,480 6 See below 7 8 55.0 7.0 — — 168 — —13,404 9 55.0 — 7.0 — — 77 1.00 7,720 10 Mixture/(Comp. Ex. 8 and 9)(90/10) — — 11 Mixture/(Comp. Ex. 8 and 9) (50/50) — — 12 Mixture/(Comp.Ex. 8 and 9) (30/70) — — 13 Mixture/(Comp. Ex. 8 and 9) (10/90) — — 1455.0 2.2 4.8 — 0.14 53 53 0.53 9,506 15 — — — — — — — — 6 55.0 168 420.20 13,887 7 55.0 77 42 0.35 10,338

[0132] TABLE 3 Antifoaming Test Density Storage Test Density After 40°C./2 Compatibility Test Viscosity Practical (Initial) days) Afterincrease after Overall Example. g/cm³ g/cm³ Initial 40° C./2 days 40°C./2 days Performance 1 1.08 1.07 ∘ ∘ ∘ Passed 2 1.03 1.06 ∘ ∘ ∘ Passed3 1.00 1.01 ∘ ∘ ∘ Passed 4 0.99 0.96 ∘ ∘ ∘ Passed 5 1.06 1.04 ∘ ∘ ∘Passed 6 1.02 1.01 ∘ ∘ ∘ Passed 7 1.02 1.02 ∘ ∘ ∘ Passed 8 1.00 0.98 x ∘∘ Passed 9 0.95 0.96 ∘ ∘ ∘ Passed 10 1.06 1.03 x ∘ ∘ Passed

[0133] TABLE 4 Antifoaming Test Density Storage Test Density After 40°C./2 Compatibility Test Viscosity Overall Comp. (Initial) days) Afterincrease after Performance Example g/cm³ g/cm³ Initial 40° C./2 days 40°C./2 days Jugemen 1 1.06 0.91 x ∘ ∘ Failed 2 0.92 0.92 x x ∘ Failed 30.89 0.85 x x ∘ Failed 4 0.89 0.82 ∘ ∘ ∘ Failed 5 0.93 0.85 ∘ ∘ ∘ Failed6 1.10 0.82 x ∘ x Failed 7 1.03 0.84 ∘ ∘ x Failed 8 1.09 1.07 x x ∘Failed 9 0.80 0.80 ∘ ∘ ∘ Failed 10 1.09 1.05 x x ∘ Failed 11 1.07 1.03 xx ∘ Failed 12 1.04 0.99 x x ∘ Failed 13 0.94 0.88 ∘ ∘ ∘ Failed 14 0.830.82 ∘ ∘ ∘ Failed 15 0.82 0.82 ∘ ∘ ∘ Failed

Industrial Applicability

[0134] The silicone antifoaming agent of the present inventiondemonstrates excellent antifoaming effect in aqueous foaming systems.When this agent is added to ink, it significantly suppresses developmentof cissing during use of the ink.

1. A silicone antifoaming agent comprising a polyoxyalkylene-modifiedsilicone characterized in that the polyoxyalkylene-modified siliconecontains 10 to 200 diorganosiloxane units per molecule and haspolyoxyalkylene-modifying group expressed by general formula—(CH₂)_(r)-O—(C₃H₆O)s-Q  (1), where Q is a hydrogen atom, or amonovalent organic group selected from an alkyl group having 1 to 18carbon atoms, an acyl group, an amino group that can be substituted, oran —N═C═O group, r is a number from 2 to 6, and s is a number from 5 to50, and polyoxyalkylene-modifying group expressed by general formula—(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′  (2), where Q′ is a hydrogen atom, or amonovalent organic group selected from an alkyl group having 1 to 18carbon atoms, an acyl group, an amino group that can be substituted, oran —N═C═O group, r′ is a number from 2 to 6, and s′ is a number from 1to 30, said polyoxyalkylene-modified silicone satisfying the followingconditions: 3≦E≦90 and 0.01≦E/(E+P)≦0.45, wherein P is the total numberof oxypropylene units (—C₃H₆O—) and E is the total number of oxyethyleneunits (—C₂H₄O—) per molecule.
 2. The silicone antifoaming agent of claim1, wherein said polyoxyalkylene-modified silicone is expressed by thefollowing general formula R¹ _(3-a)G¹_(a)SiO—(R¹R¹SiO)_(x)-(R¹G²SiO)_(y)-(R¹G³SiO)_(z)-SiG¹ _(a)R¹_(3-a)  (3) where G¹ is a group selected from R¹, G², or G³, which canbe different, and R¹ is independently an alkyl group with 1 to 18 carbonatoms or an aromatic group with 6 to 9 carbon atoms; G² is a groupexpressed by the following formula: —(CH₂)_(r)-O—(C₃H₆O)_(s)-Q where Qis a hydrogen atom or a monovalent organic group selected from an alkylgroup having 1 to 18 carbon atoms, an acyl group, an amino group thatcan also be substituted, or an —N═C═O group, r is a number from 2 to 6,and s is a number from 5 to 50; G³ is a group represented by thefollowing formula: —(CH₂)_(r′)-O—(C₂H₄O)_(s′)-Q′ where Q′ is the same asQ, r′ is a number from 2 to 6, and s′ is a number from 1 to 30); x is anumber from 10 to 200, y is a number from 0 to 60, z is a number from 0to 30, and, a is 0 or 1.